April 8, 2011 -- Vegetarians have a reputation for being ''heart healthy.'' However, a new report says some vegetarians may be increasing their risk of heart problems from nutritional deficiencies in their diets.

Overall, meat eaters are still at higher risk of heart attacks and strokes compared to vegetarians, says researcher Duo Li, a professor of nutrition at Zhejiang University in Hangzhou, China.

But in his review of published articles from medical journals, he found that vegetarian diets are often lacking in some key nutrients. These include vitamin B12 and omega-3 fatty acids. The deficiencies were especially evident, he says, in vegans. Vegans don't eat meat, fish, or any kind of animal product, including eggs and milk.

The deficiencies in B12 and omega-3, in turn, are linked with higher blood levels of an amino acid called homocysteine. The deficiencies are also linked with decreased levels of HDL cholesterol, the so-called good cholesterol, he says. High homocysteine levels have been suggested as a risk factor for heart disease. Higher HDL levels are heart protective.

"This may be associated with an increased thrombotic [blood clot] and atherosclerotic [hardening of the arteries] risk," he tells WebMD.

However, other nutrition experts say many vegetarians are already aware of the need to pay close attention to intake of vitamin B12 and omega-3s. They say the increased risk to heart health that Li suggests is only a hypothesis.

The study is published in the Journal of Agricultural and Food Chemistry.